Steerable follower selection mechanism

ABSTRACT

A selection mechanism is disclosed which employs a controlled steerable follower for selecting and following a cam groove in a barrel cam to cause relative translation between the barrel cam and the cam follower. The motion of the barrel cam while translating is converted into rotary motion to rotate a single element on a single element printer to accurately position a selected row of characters adjacent the print point. A similar follower is used to cause translational movement of the tilt cam and a bell crank and link arrangement is used to translate the lateral movement of the tilt cam to the type element. The control of the rotate cam follower is electro-mechanical wherein a signal is converted by a linear motor into a mechanical movement at a desired time within a cycle and thus dictates the selection to be made, when combined with an electrical signal to a solenoid for selecting the direction of rotation to which the cam translatory movement is to be converted. Means are disclosed which allows absorbing within the mechanism, of inertia shocks, such that the parts of the device may be made smaller and still withstand the forces required for selection.

United States Patent [191 Schaefer [451 May 27, 1975 STEERABLE FOLLOWER SELECTION MECHANISM [75] Inventor: John O. Schaefer, Lexington, Ky.

[73] Assignee: International Business Machines Corporation, Armonk, NY.

221 Filed: Dec. 26, 1973 21 Appl. No.: 427,882

Primary ExaminerEdgar S. Burr Assistant Examiner-Paul J. Hirsch Attorney, Agent, or Firm-Laurence R. Letson [5 7 ABSTRACT A selection mechanism is disclosed which employs a controlled steerable follower for selecting and following a cam groove in a barrel cam to cause relative translation between the barrel cam and the cam follower. The motion of the barrel cam while translating is converted into rotary motion to rotate a single element on a single element printer to accurately position a selected row of characters adjacent the print point. A similar follower is used to cause translational movement of the tilt cam anda bell crank and link arrangement is used to translate the lateral movement of the tilt cam to the type element.

The control of the rotate cam follower is electro-mechanical wherein a signal is converted by a linear motor into a mechanical movement at a desired time within a cycle and thus dictates the selection to be made, when combined with an electrical signal to a solenoid for selecting the direction of rotation to which the cam translatory movement is to be converted.

Means are disclosed which allows absorbing within the mechanism, of inertia shocks, such that the parts of the device may be made smaller and still withstand the forces required for selection.

7 Claims, 7 Drawing Figures PATENTEB MAY 2 7 i975 SHEET FIG. 3

FIG. 6

SHEET KEYBOARD 1 2 CONTROL LOGIC FIG. 4

@FIG. 7

ROTATE LINEAR MOTOR TILT MAGNET RACK SWITCH SOLENOID STEERABLE FOLLOWER SELECTION MECHANISM BACKGROUND OF THE INVENTION As single element printers develop, efforts continue to simplify the selection mechanism by which control is exerted on the print element and thereby make the mechanism lighter and more responsive so that it can be totally packaged within the print element carrier. This simplification lends itself to implementation when a typewriter uses electronic logic to control the selection functions.

In view of the relatively high speed at which single element printers print, it is necessary to design substantial strength into the parts of the print mechanism so that they may withstand inertia forces during the print operation. It is also desirable to reduce the bulk and weight of the selection mechanism and thus the print carrier to accomplish a reduction in forces and power required to operate the typewriter or printer.

Barrel cam control arrangements have been disclosed in the past which involved multiple pin latch assemblies or a multiple latch assembly with a single pin controlling depth of pin insertion to control character selection.

The mechanisms are relatively expensive due to either the precise control necessary in controlling the depth of the selector pin and cam expense or the extent of duplication of similar mechanisms where a separate latch, electromagnet, and selector pin assembly is required for each possible increment of rotate selection.

Further, for higher print speeds, it is necessary to reduce to a minimum weight of component parts to overcome their inertia so that the print speeds can be accomplished reliably at above what is normally considered typewriter printing speeds today.

OBJECTS OF THE INVENTION It is an object of this invention to reduce the size, strength, and complexity of the selection mechanism of a barrel cam selection device for a single element typewriter.

It is another object of this device to absorb the shocks and forces exerted during high loading periods to enable the reduction of size and strength of parts encountering such forces.

It is still another object of this invention to select rows of characters on a print element on a single element printer, by the control of a single steerable follower in a multi-branched channel barrel cam assembly. 7

It is an additional object of this invention to select the character desired on a single print element of a single print element printer, by the control and actuation of two deflectable cam followers engaged with two multibranched barrel cams.

The foregoing and other objects, features, and advantages of the invention will be apparent from the following more particular description of a preferred embodiment of the invention as illustrated in the accompanying drawings.

THE DRAWINGS FIG. 1 illustrates a typewriter with a single element or single print element operationally mounted on a print carriage for translation across the printing page.

FIG. 2 is a partially exploded perspective view of a print mechanism employing the invention where the selection is accomplished by the barrel cams acting through follower mechanisms to control the printhead.

FIG. 3 is a bottom plan view of the control cam and followers together with the drive arrangement of the carrier.

FIG. 4 is a developed plan representation of the cam surfaces of the tilt cam.

FIG. 5 is a developed plan representation of the cam surfaces of the selection cam and the control cam in parallel with correspondingly timed cam surfaces correlated by the horizontal timing lines.

FIG. 6 is the restore and resynchronization cam for returning the barrel cam to its home position in the event of malfunction and to control the rotate cam during rack switch.

FIG. 7 is a schematic logic diagram of the type logic used to control the mechanism illustrated in FIG. 2.

SUMMARY OF THE INVENTION The above objects of the invention and the advantages over the prior art are accomplished by the use of a positively controlled steerable follower mechanism which permits the selective engagement of the follower with a particular path in a barrel cam under the control of the keyboard to provide a translational motion of the barrel cam which may then in turn be converted into a rotary motion of the type element as is described in US. patent application Ser. No. 375,277, filed June 29, 1973, in the name of Iraj D. Shakib, and commonly assigned with this application. The control of the direction of motion of the type element is controlled by the engagement and disengagement of the teeth of a double sided alternately engageable rack member as described in. the above patent application.

The above application also describes the use of a multi-branched channel barrel cam to provide lateral translation as described above.

The control of the amount of lateral translation of the barrel cam is made through physically controlling the angle of a deflector/follower and the time at which the follower is caused to deviate from a normal path. To accommodate the relatively high loads involved in the deviation from the normal path, a shock unloading or absorbing system is provided to minimize the forces involved in causing translation of the barrel cam. Control of selection of the row as well as the column of a character is accomplished by means of a follower capable of being diverted into a particular cam profile path.

DETAILED DESCRIPTION OF THE INVENTION FIG. 1 illustrates a typewriter provided with a keyboard. The typewriter is of the single element type wherein a print carriage 14 is slidably mounted on support members 16 which also serves as a drive connection for the carrier, for reciprocal motion laterally across the typewriter 10. Immediately behind carriage 14 is platen 18 which holds a copy sheet 22. Mounted on carriage 14 is print element 20 which is capable of being impacted onto copy sheet 22 and against platen 18 to effect printing.

Referring to FIG. 2, a carrier frame 24 is illustrated in a broken-away fashion. Carrier frame 24 contains holes through its side frame through which support and print shaft 16 of FIG. 1 extends. Print shaft 16 likewise extends through print sleeve 26. Print sleeve 26 provides a smooth cylindrical exterior surface for control cam 28. Control cam 28, its cam surfaces and function will be discussed more completely below. Print shaft 16 extends through hole 30 in side frame 24. Also mounted on side frame 24 is double acting linear motor or actuator 32. Double acting linear motor 32 is connected electrically to the logic and timing circuitry of typewriter 10. This connection is accomplished through control leads 34. Double acting linear motor 32 provides the mechanical push pull input to control the steerable follower in thecarrier.

To provide the push pull input to the steerable follower mechanism, link 36 is attached to the armature of linear motor 32. Link 36 is also connected to follower pin 38 through locking collar 40. This provides an attachment means for pin 38 to solenoid link 36. In order to transmit the lateral motion of pin 38 from its path to cam follower 42, a yoke member 44 engages with its bifurcated end, pin 38. Yoke member 44 is then fixedly attached to pivot shaft 46 to convert the oscillatory motion of fork 44 to an oscillatory motion of pivot shaft 46 on which rotate cam follower 42 is fixedly mounted. Restoration to a normal undeflected position is provided by bifurcated spring 48 which acts to restore rotate cam follower 42 to its undeflected position. Additionally, leaf spring 50 is provided with a spring depression 52 which provides a valley into which the bearing for pivot shaft 46 rests thus providing a nomi nal or relaxed position corresponding to a home position for pivot shaft 46 and the pivot point of rotate cam follower 42.

A safety release is provided so that in the event cam follower 42 should come out of any of the grooves in the barrel cam 54, the follower can ride up over the external periphery of the barrel cam 54 and thus not break either the follower or the cam. This safety release mechanism is in the form of a lead spring 56 which is biased against the end of pivot shaft 46 normally holding follower 42 in the grooves of barrel cam 54.

Pivot shaft 46 is supported upon rocker member 58 which is in turn pivotally supported on pivot pin 60. Rocker 58 pivoting around its pivot point 60, through its uplifted arms 62 and 64, provides for a lateral translation of pivot shaft 46 and rotate cam follower 42. To accommodate follower pin 38, an elongated slot 66 is provided in the upper end of rocker arm 64. A positioning follower pin 68 is fixedly attached to the rocker arm 64.

To convert rotary motion to linear motion in preselected increments of linear displacement, a keyed drive shaft 70 is rotatably supported in carrier end frames 24. Mounted in mating relation on the keyed shaft and slidable coaxially therewith is a barrel cam 54 with grooves or cam surfaces formed in the periphery thereof such that they dictate, by individual engagement with a cam follower 42, lateral displacement corresponding to preselected increments of distance, which may be converted into rotary motion of a type element 20. This conversion of any lateral motion of barrel cam 54 is accomplished through the engagement of rack follower groove 72 by rack follower 74. Rack follower 74 is fixedly attached to or formed as an integral part of bifurcated rack member 76. Bifurcated rack member 76 is pivotally mounted on rocker pivot 78 to allow engagement alternatively of one rack or the other of rack member 76. Alternate engagement of rack members 76 are accomplished by push pull solenoid 80 connected to an engagement tab 82. This connection isaccomplished through link 84 which is adapted as a lost motion link allowing link 84 to slip through tab 82 until stopped by stop members 86 thus providing a range of movement of link 84 prior to the engagement of tab 82. This insures that solenoid may relax between actuations and not disturb the position of rack member 76. The rack teeth on rack 76 are alternatively engageable with pinion 86 which in turn drives rotate shaft 88 and controls the rotational position of type element 20 in accordance with the technique disclosed in Ser. No. 375,277, referred to above.

To provide control of rocker 58 and follower 42. control cam 28 is provided with three channels formed in its periphery. Control cam 28 is slidably mounted on print sleeve 26 which may be alternatively referred to as a support sleeve. The cam is allowed to translate on the sleeve 26 in a longitudinal fashion and is keyed to rotate with the sleeve 26. Key slot 90 is provided in the sleeve 26 to provide an attaching surface in the sleeve 26.

The slot 98 or cam surfaces 96, in the periphery of control cam 28 are such that they permit movement or restrict the relative movement of the associated followers and in so doing, guide their followers into controlled positions.

Attached to or a part of support member 92 is a follower tab 94. Follower tab 94 is normally continously engaged in cam 96. Cam 96 is provided with a varying width to allow control cam 28 to shift laterally in certain predesignated regions and then return to a predetermined position in other certain predesignated regions of rotation of print shaft 16.

Positioning follower pin 68 is engaged with parallel sided groove 98 and either moves cam 28 in response to the movement of upper rocker arm 64 about its pivot point 60 on support member 92 or, in reverse, acts on pivot or follower positioning pin 68 in response to the change of the width of cam groove 96 and its engagement with follower tab 94. Cam groove 100 is a varying width cam groove to allow follower pin 38 some translational freedom of movement at predetermined portions of a printing cycle, and provide profiles which act to guide follower 42 into cam grooves in cam 54. The relationship of the cam groove widths to each other and to the tracks or cam grooves that branch from the main channel in the rotate barrel cam 54 are illustrated in FIG. 5. The two cams are laid out in surface development in parallel to provide corresponding points on all surfaces in parallel or on the same reference line. The

reference lines and degree markings are arbitrary but used to ease understanding.

Referring now to FIG. 5, cam 54 is illustrated onthe left while cam 28 is illustrated on the right. For ease in understanding, cam groove 100 has been broken into a number of subregions and each subregion will be identified and explained. Groove 100 really consists of a channel with two facing cam surfaces, one on the right and one on the left. The respective portions of the channel have been designated 99 for the left portion of the channel and 101 for the right portion of the chan nel. Only one side of the channel or one cam surface is engaged with follower 38 at any one time. Therefore, it can be considered that cam groove 100 consist of a depression in the cam and two different cam surfaces. This explains the non-symmetry of the respective surfaces. The brackets encompassing portions of the cam surfaces which make up cam groove 100, are used for convenience in identifyingportions of the overall cam profile for discussion.

Referring to cam groove 100, the cam surfaces on the lefthand side of this cam groove as viewed in FIG. 5 control the follower when it is being engaged with cam grooves 152, 154, and 156 of cam 54. The surfaces on the righthand side of cam groove 100 control the follower when it is being engaged with grooves 151, 153, and 155.

Surfaces 202 and 204 are straight parallel surfaces which provide freedom of movement for pin 38 laterally and allowing that lateral movement to translate into a pivotal movement of follower 42. Surfaces 202 and 204 are displaced from the centerline or restricted path of groove 100 such that follower 42 may be deflected to enter cam groove 156 or 155 respectively. Surfaces 206 and 208 provide for a sharper or wider deflection of follower 42 to allow proper entry into cam groove 154 or 153 respectively of cam 54. Surfaces 210 and 212 of cam groove 100, acting on follower 38, control the optimism entry angle of follower 42 with respect to cam groove 152 and 151 respectively.

Surfaces 218 and 220 act to return the follower to an undeflected position or steer it after entry into cam grooves 152 and 151 respectively and thus prevent wedging of the follower 42 in these grooves. Surfaces 218 and 220 also act to restrict the available movement of follower 42 in a pivotable motion and thus act to steer the follower into the dwell or straighter region of all of the branched cam surfaces. This prevents wedging and the breaking of the follower or cam.

The sharp shoulders between segments 218 and 222 of the lefthand cam surface and segments 220 and 224 of the righthand cam surface provide a transistional point where the groove is widened and allows follower 42 freedom of motion during the period when selected is being completed and oscillations and vibrations inherent in the mechanical mechanism are settling prior to print. Regions 222 and 224 provide relatively unrestricted follower movement and pin translation ,for pin 38. Surfaces 226 and 228 act to guide follower 42 into a relatively nominal or straight position upon their exit from groove 153, 154, 155, and 156. The need for this repositioning of the follower is such that a follower coming out of groove 153 could conceivably wedge in the relatively large open area where 153 joins 150 and at the same point groove 154 is joining 150. If the follower wedges at that point, either the cam or the follower could possibly be broken.

Region 230 and 232 merely restrict the lateral movement of pin 38 thereby maintaining follower 42 in a straight or undeflected position during the single groove portion ofcam 54. Surfaces 234 and 236 merely act as relief surfaces broadening the channel to allow follower 42 to be deflected and activated for selection of either cam groove 156 or 155.

Surfaces 230, 232, 234 and 236 are not essential because spring 48 acts to restore the follower 42 to its undeflected position when the cam 54 is not acting on it.

Referring now to cam groove 96, this groove is formed by cam surfaces 95 and 97. Surfaces 95 and 97 are generally symmetrical and act to release cam 28 from a confined position and allow it to move under the influences exerted on it by pin 68. In the region extending from generally of rotation to approximately 160 of rotation, it can be seen that the channel is relatively wide and open to provide maximum movement with respect to tab 94. Tab 94 must be restricted into a fairly narrow channel by the time the carrier is ready for print, and therefore the channel is narrowed by converging surfaces 95 and 97 generally in the region of 160 through 190. Print occurs roughly at 215 to 220 of rotation of cams 54 and 28. As you can see tab 94 is restricted at that point between the narrowed walls 95 and 97 and therefore fairly accurately position cam 28 with respect to tab 94.

Referring now to FIG. 2, the selection of the amount of tilt of the typehead is controlled by the degree of lateral movement of tilt barrel cam on keyed shaft 70. The degree of translational movement of tilt barrel cam 110 is controlled by tilt cam follower 112 which may be diverted into one of the three tracks in the periphery of tilt barrel cam 110. Tilt barrel cam follower 112 is pivotally supported upon extensions 114 and 116 of support member 92. Also supported on support member 92 is electromagnetic latch coil 118. Extending across the end of the coil core is latch armature 120. Latch armature 120 is supported by support member 122 and 124 for limited motion perpendicular to the axis of the core of electromagnetic latch coil 118. The activation of an electrical current through coil 118 will cause attraction of armature 120 and the relaxation of the current through coil 118 will allow restoration of the armature under spring bias from spring 126.

For control of shaft 113 and follower 112, latch 128 is fixedly attached to pivot shaft 113 of cam follower 112. Latch 128 is provided with two depending arms, spring arm 130 and latch arm 132. Spring arm is spring biased by a spring 134 which is tensioned by attachment between spring arm 130 and a grounded tab 136 which may be formed as part of armature support 124 or may be formed as part of the support frame 92.

By activation of the solenoid upon introducing a current through the coil 118 an the attraction of armature 120 against the force of spring 126, the outboard end 121 of armature 120 is disengaged from latch arm 132 allowing cam follower 112 to rotate under the influence of spring 134. This provides follower 112 with a deviation from its nominal or restored path and may enter the next groove of tilt cam 110 presenting itself to cam follower 112. The groove selected will depend upon the timing of the actuation of armature 120 by the control of the relative time at which the current in coil 118 is established.

As the follower 112 travels down the fall of the cam groove after the high dwell of cam 110, the pivoting of the follower in the opposite direction will allow spring 126 to restore armature 120 to its raised position allowing outboard end 121 to engage latch arm 132 and thereby maintain cam follower 112 in its undeflected position until a subsequent signal is received in the form of a current in electromagnetic coil 118.

The lateral translation of cam 110 up and to the left as shown in FIG. 2 can be translated through a follower and bell crank/link arrangement to effect the tilting of type element 20, in an analogous fashion to that illustrated in US. patent application Ser. No. 375,277 referred to above.

Referring to FIG. 3, it can be seen that a timed relationship between the rotation of print shaft 16, print sleeve 26, and control cam 28, all driven by print shaft 16, and gear 140 exists, which in turn operates through idler 142 and drives cam shaft gear 144. The drive ratios are selected such that one rotation of print shaft 16 results in one identical rotation of keyed shaft 70 and the barrel cams mounted thereon.

The engagement of tab 94, pin 68, and pin 38 with the cam grooves 96, 98 and 100 respectively of control cam 28 are more clearly illustrated in FIG. 3. 1

It can be seen that in the position which cam 28 assumes in FIG. 3 as illustrated, an actuation of linear motor 32 would not result in any motion inasmuch as pin 38 is blocked from lateral motion by the sides of control groove 100.

As can be seen from the position of cam 28 in FIG. 3, tab 94 which is the locating tab is in the narrow portion of groove 96 thus laterally restricting the position of cam 28. By laterally restricting the position of cam 28, pin 68 is laterally restricted in its location and therefore controls the upper arm 64 of rocker 58 and therefore positions the cam follower bearing in its center or rest position at the bottom of spring depression 52.

Referring now to FIG. 4 and 5, the surfaces of cam 110 and earns 54 and 28 have been developed into planar developments such that the relative positions of the cam profiles may be correlated. The developments of FIG. 4 and cam 54 of FIG. 5 are made in such a way that as one progressively tracks the cam surface under the followers 112, 42, it is apparent that at the point where the follower 112, 42 is diverted to force it into a selected track or at least in the regions where it can be forced into a selected track, the cam groove 100 of cam 28 is wide, allowing the follower pin 38 to be deviated from its center line or home position and thereby translate bifurcated fork member 44 to cause follower 42 to deviate into the desired track. At the same time that the track 100 is wide and allows the selection of the track by follower 42, track 96 opens up to permit lateral translation of cam 28 with respect to sleeve 26. Inasmuch as tab 94 and pin 38 then do not control the position of the cam, any movement of positioning follower pin 68 will cause cam 28 to slide longitudinally on sleeve 26. Since any movement of pin 68 is caused by a deviation from the normal position of follower 42 and pivot shaft 46, this allows a shock absorbing system where the follower 42 is forceably deviated from its rest position and the inertia of cam 54 tends to move the follower as opposted to allowing the follower to remain fixed. This allows a translatory time during which cam 54 may be accelerated from its translational rest position and then be finally positioned by the action of control cam 28 restricting the points which tab 94 and follower 68 can assume during the printing portion of a cycle. Groove 96 will narrow to a parallel groove which accurately positions control cam 28 with respect to. tab 94 and hence restricts the position of follower pin 68. By so doing, rocker assembly 58 is caused to assume a predetermined defined position thus fixing spacially, with respect to the carrier 14, the pivot point of follower 42. By so doing, cam 54 then becomes relatively positioned and in turn causes a known translational incremental movement of rack member 76 to rotate type element 20 a preselected desired amount, depending on which groove follower 42 entered. During periods of the cycle where high loads on relatively small weak parts are encountered, freedom of translational movement of control cam 28 is allowed. During those portions of the cycle where positions must be accurately defined, the cam surfaces 96 and 100 of the control cam 28 narrow to restrict the possible positions of the cam and its respective follower Thus it=can beseen lored to provide an optimum entry angle of follower 42 i into the branched grooves in barrel cam 54 and to provide a steering and guiding action to the follower42 after it has entered the grooves. with respect to the one unit displacement which is identified as' cam groove 151 in FIG. 4, it is necessary to steer the follower after entry such that it will not wedge in the groove. Thisis accomplished by the cam profile 212, 216 illustratedat 160 in FIG. 5. This particular profile tends to straighten the follower out shortly after entering cam groove 151 thereby preventing wedging of the follower 42 in the cam groove.

For cam grooves 152 through 156, the angle of entry is controlled by groove of cam 28, however the angle with respect to the cam groove is such that a positive steering after entry is not required. The steering is accomplished by the restricting of the movement of follower pin 38 and guiding it back toward the centerline of cam groove 100 thereby tending to restore bifure cated fork 44 to its center rest position and restoring the follower 42 to a position which is generallypa'rallel with cam groove 150.

As can be seen from studying the cam profiles of cam 54, the selection of which groove the follower will enter and follow, is determined by the time in the cycle at which point the linear motor 32 is activated electrically to cause a deflection of the follower. Selection of the appropriate groove will determine the units of displacement from the home position that cam 54 will translate and at the same time determine a direction of translatron. In order to accomplish selection on a typeelement containing 24 columns of characters, it isnecessary to double the rotational responses to the six translational responses possible from the cam. This doubling is accomplished by means of the bifurcated. rack 76 being alternatively engageable with pinion 86 to provide both negative and positive rotation of the head. It should be apparent from referring to FIG. 2, that the rack teeth on one side of rack 76 will cause both positive andnegative rotation of the typehead depending upon which cam grooves are selected by follower 42. The term posltive and negative rotation of the typehead can be assigned arbitrarily and as long as it is maintained does not have a bearing upon the operation of the mechanism. A positive and negative rotation can refer, for example, to clockwise and counterclockwise rotation of the print head 20. i

It should also be readily apparent that by switching to the alternate set of teeth on rack 76, the same groove on cam 54 can provide rotation in the opposite direc-.

tion and thus effectively double the selectioncapabilities in cam 54.

The inputs required to carrier 14 to make a character column selection is an input to linear motor 32 at a predetermined desired time to cause follower 42 to deviate into one of the selection grooves 150 through 156 and a signal to solenoid 80 to engage the appropriate set of teeth on rack 76 to cause the appropriate positive or negative rotation of typehead in response to the translational motion of cam 54.

To select the row on the typehead, an electrical signal is transmitted to electromagnetic latch coil 118 at a selected time in the operational cycle of the printing mechanism to attract armature 120 and thereby release latch arm 132 and allow cam follower 112 to enter one of three grooves 171-173. Surface 170 is a straight cylindrical surface and represents one-half of a zero tilt cam groove with no axial deviations. By controlling the timing of the electrical pulse to coil 118, cam follower 112 is controlled and deviated into one of the desired tilt grooves 171 through 173 or allowed to remain in the case of no electrical signal in an undeviated position riding parallel with surface 170. The translation motion or lack thereof of cam 110 is transmitted through conventional bell crank and link arrangements to cause the tilting of typehead 20 in a manner analogous to that disclosed in U.S. patent application Ser. No. 375,277 referred to above. The exact linkage is not disclosed inasmuch as that does not constitute part of this invention.

In the unlikely event that follower 42 is caused to ride up over the periphery of cam 54 and the barrel cam is thus without control, a restore and resynchronization cam 180 is provided. The restore and resynchronization cam 180 is illustrated in FIG. 6. The cam is in the form of a concave cylindrical surface with a locating and restoring funnel-shaped or V-shaped path 182 cut into the interior cylindrical surface of the cam 180. Cam 54 is provided with a restore pin for engagement with path 182. Restore pin 184 is illustrated in FIG. 4 as well as in FIG. 3 and 6. The entrance to restore path 182 is sufficiently wide to accommodate pin 184 at any of its possible deviations and narrows progressively to a position which will allow cam follower 42 to re-enter groove 150 at the time that pin 184 exits from the narrowest portion of path 182. It can therefore be readily observed that in the event that cam follower 42 is inadvertently caused to ride out over the periphery of cam 54, only one cycle will be improper prior to the automatic restoration of the follower into the cam surfaces and re-engagement for further operation. A further function of restore cam 180 is to provide home position location of barrel cam 54 during the period of time allocated for shifting rack 76 to engage the other set of teeth, any time the opposite direction of rotation is required.

OPERATION As an example, a key is depressed on keyboard 12 of typewriter 10. This information is converted into electrical signals by the electronic circuitry of the typewriter. At the same time a mechanical cycle clutch (not shown) is caused to start the rotation of print shaft 16. At the appropriate time during the cycle, depending upon the preselected character which for example has a position of typehead 20 of a 2 rotate and a 2 tilt, signals are sent to the linear motor 32 such that link 36 is extended to move rocker fork 44 in a counterclockwise direction as viewed in FIG. 2. The rocking action of fork 44 in a counterclockwise direction rotates follower 42 in a counterclockwise direction.

The timing of the signal to linear motor 32 and thus the twisting and rocking of follower 42 is accomplished at the time when the follower cannot enter groove 156 or groove 154 but has yet to engage 152. At the time that the keyboard selection, through the electronic logic of the typewriter, selects the timing for the signal to linear motor 32, it also makes a decision and provides a signal to solenoid to cause solenoid 80 to either extend or retract to engage the proper rack of rack member 76. Inasmuch as the racks may not be conclusively labeled plus or minus, it is arbitrary which rack is engaged so long as the denotation is maintained constant and the appropriate denotation is carried through and correlated to the motion generated by the engagement of the follower with selected grooves of cam 54.

The tilting of the typehead 20 is accomplished by the picking of armature 120 at a time when follower 112 has progressed past groove 173 and is approaching groove 172. If latch armature 120 is picked at that time, follower 112 will deviate under the influence of spring 134 into groove 172 thus causing a 2 unit translation of cam leftward as is viewed in FIG. 2. Through the conventional bell crank and link arrangement as discussed earlier, the typehead is caused to tilt 2 units. This accesses the number two row of characters which combined with the 2 unit rotate as previously described selects the character which corresponds to the key on keyboard 12 which was depressed.

At this point the cams dwell in their translational movement due to the dwell portion of the cam groove providing a zero lateral translational movement with respect to follower 1 12 and 42 respectively. It is during the very last portion of this part of the cycle that the impacting of typehead 20 against platen 18 is accomplished. If copy sheet 22 is between platen l8 and typehead 20, an imprinting of a character will occur.

The print cam and follower operation is that described in patent application Ser. No. 375,277 and does not form a part of this invention and is therefore not described in detail herein.

After the print operation has occurred, the cam profiles 152 and 172 restore the cams to their restored or non-translated positions with respect to followers 42 and 112 respectively. At these times, the followers are twisted back to their original non-deflected positions and follower 112 is latched in this position through the action of restore spring 126 acting on armature to block latch arm 132.

Spring 4-8 and 50 act to return follower 42 to its undeflected home position.

At the time when cams 110 and 54 are at their high dwell which corresponds to the time for printing, the cam grooves 96 and 98 are approximately as wide as the followers engaged therein. This restricts the movement of cam 28 and therefore accurately positions rocker 58 through the restricted position of pin 68. This in turn accurately positions follower 42 and cam 54 to give the desired position to rack member 76.

Case shift is accomplished by selecting of groove 156 by follower 42, and at the high dwell energizing solenoid 80 to switch rack 76 to the opposite set of teeth. This action adds the rise and fall of cam 54 to secure 12 units of rotation, thus shifting case. During this shift operation, the carrier is conditioned for no-print as is described in US. patent application Ser. No. 375,277.

Referring to FIG. 7, for an understanding of the logic control of the typewriter 10, print shaft 16 is coupled to emitter disk 202. Emitter disc 202 has magnets attached at angular positions corresponding to the start of times for activation of linear motor 32 and coil 118.

Control logic 200 is connected to receive signals from the Keyboard and determine which rack position is required to rotate the head to the desired character row, the direction of deflection required of follower 42, and the time of activation of coil 118 and linear motor The time dependent signals are controlled by emitter wheel outputs. These outputs are signals from magnets 2'04, 206, 208 to the control logic. The control logic is capable of using the timing pulses from the magnets 204, 206, 208 to allow the signals to magnet 118 and linear motor 32 to be sent such that non-selected grooves of cams 54, 110 have passed followers 42, 112 when the signals are transmitted. Thus, if a character needs a 3 unit rotate signal the second pulse from the emitter 210 would allow the signal to be sent to linear motor 32 together with a polarity to control the direction of the motors reaction. The tilt timing is analogous to the rotate timing.

Rack switch is not time dependent as the rotate and tilt function is and occurs at the time the signal is ready to be sent from the logic 200 to solenoid 80.

While the invention has been particularly shown and described with reference to a preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein with departing from the spirit and scope of the invention.

1 claim:

1. Selection apparatus for selecting a character on a single type element of a single element printing mechanism, comprising:

a cam control means having a single groove branching to form a plurality of branch grooves and said branch grooves terminating in said single groove;

means for rotating said cam control means through a complete revolution and returning said cam con trol means to a predesignated position;

a follower for engagement with said cam grooves;

means for deflecting said follower from said single groove to cause said follower to enter a selected one of said branches to cause relative axial motion between said cam and said follower along the axis of said cam;

said follower returning to said single groove when said control cam means is in said predesignated position;

means engaged by said cam control means to convert said caused relative motion to a rotational movement of said type element in accordance with and corresponding to the one of said grooves selected by said follower.

2. A selection apparatus for selecting and positioning a desired row of characters on a single element in correspondence with a print point on a single element printing mechanism, said apparatus comprising:

a cylindrical shaped cam with a plurality of connecting cam grooves formed into the cylindrical surface thereof;

an annular groove formed into the cylindrical surface of said cam;

a controllable, deflectable follower vane engaged with one of said cam grooves;

control means to cause deflection of said follower vane and to cause said vane to enter one of said cam grooves;

means for drivingly rotatably supporting said cam for rotation with respect to said follower to create relative axial motion betweem said cam and said follower;

means for fixing said follower spacially with respect to said cam means;

means for engaging said annular groove and to move with said annular groove through movements in a direction parallel with the cylindrical axis, of said cam;

means for receiving said movement and converting said movement to a rotary incremental motion corresponding in amount to the amount of said movement;

means for releasing said follower from its defined spacially fixed position for limited movement in a direction along the direction of said cam movement;

means for repositioning said follower fixed position; 1

whereby said cam follower causes said cam to translate axially and create closely controlled displaceat said spacially ment of said movement to rotational motion con-.

version means and the forces encountered during the deflection of said follower into one of said grooves are allowed to translatesaid follower and thus dissipate, thereby reducing the stresses within said selection apparatus.

3. The apparatus of claim 2 wherein said control means for controlling the said follower acts in timedrelation to the relative rotational movement of said ca with respect to said follower.

4. The apparatus of claim 2 wherein said means for repositioning said follower comprises a control cam means for positively constraining said follower to said spacially fixed point in timed relation to said revolution of said cam means. i i 1 5. The apparatus of claim 4 wherein said means for repositioning further comprises a spring means for continuously urging said follower to said spacially fixed position.

6. The apparatus of claim 4 further comprising cam V means to control the direction of the followerwhen de flected, to provide steering of the follower into the selected one of said grooves.

7. The apparatus of claim 2 further comprising? a second cylindrical cam means having a plurality of cam grooves formed into said cams cylindrical surface;

a second deflectable follower vane means associated with said second cylindrical cam means;

said follower vane means selectively deflectable into one of said plurality of grooves to create translation motion between said cam and said follower;

latch means for releasing said second follower vane means from the non-deflected position;

a force means connected to said second follower vane means to deflect said second follower vane means;

means for releasing said latch means in timed relation to the rotation of said last recited cam means to allow saidforce means to deflect said follower vane means to select one of said grooves;

whereby a translational movement of predetermined amount is created and made available to control the tilt of said single type element. 

1. Selection apparatus for selecting a character on a single type element of a single element printing mechanism, comprising: a cam control means having a single groove branching to form a plurality of branch grooves and said branch grooves terminating in said single groove; means for rotating said cam control means through a complete revolution and returning said cam control means to a predesignated position; a follower for engagement with said cam grooves; means for deflecting said follower from said single groove to cause said follower to enter a selected one of said branches to cause relative axial motion between said cam and said follower along the axis of said cam; said follower returning to said single groove when said control cam means is in said predesignated position; means engaged by said cam control means to convert said caused relative motion to a rotational movement of said type element in accordance with and corresponding to the one of said grooves selected by said follower.
 2. A selection apparatus for selecting and positioning a desired row of characters on a single element in correspondence with a print point on a single element printing mechanism, said apparatus comprising: a cylindrical shaped cam with a plurality of connecting cam grooves formed into the cylindrical surface thereof; an annular groove formed into the cylindrical surface of said cam; a controllable, deflectable follower vane engaged with one of said cam grooves; control means to cause deflection of said follower vane and to cause said vane to enter one of said cam grooves; means for drivingly rotatably supporting said cam for rotation with respect to said follower to create relative axial motion betweem said cam and said follower; means for fixing said follower spacially with respect to said cam means; means for engaging said annular groove and to move with said annular groove through movements in a direction parallel with the cylindrical axis, of said cam; means for receiving said movement and converTing said movement to a rotary incremental motion corresponding in amount to the amount of said movement; means for releasing said follower from its defined spacially fixed position for limited movement in a direction along the direction of said cam movement; means for repositioning said follower at said spacially fixed position; whereby said cam follower causes said cam to translate axially and create closely controlled displacement of said movement to rotational motion conversion means and the forces encountered during the deflection of said follower into one of said grooves are allowed to translate said follower and thus dissipate, thereby reducing the stresses within said selection apparatus.
 3. The apparatus of claim 2 wherein said control means for controlling the said follower acts in timed relation to the relative rotational movement of said cam with respect to said follower.
 4. The apparatus of claim 2 wherein said means for repositioning said follower comprises a control cam means for positively constraining said follower to said spacially fixed point in timed relation to said revolution of said cam means.
 5. The apparatus of claim 4 wherein said means for repositioning further comprises a spring means for continuously urging said follower to said spacially fixed position.
 6. The apparatus of claim 4 further comprising cam means to control the direction of the follower when deflected, to provide steering of the follower into the selected one of said grooves.
 7. The apparatus of claim 2 further comprising: a second cylindrical cam means having a plurality of cam grooves formed into said cams cylindrical surface; a second deflectable follower vane means associated with said second cylindrical cam means; said follower vane means selectively deflectable into one of said plurality of grooves to create translation motion between said cam and said follower; latch means for releasing said second follower vane means from the non-deflected position; a force means connected to said second follower vane means to deflect said second follower vane means; means for releasing said latch means in timed relation to the rotation of said last recited cam means to allow said force means to deflect said follower vane means to select one of said grooves; whereby a translational movement of predetermined amount is created and made available to control the tilt of said single type element. 